Embodiments of the present invention relate to a substrate support for holding a substrate in a substrate processing chamber.
In the processing of substrates, such as semiconductors and displays, an electrostatic chuck is used to hold a substrate in a substrate processing chamber. A typical electrostatic chuck comprises an electrode covered by a dielectric, such as ceramic or polymer. When the electrode is electrically charged, electrostatic charges in the electrode and substrate holds the substrate on the chuck. Typically, the temperature of the substrate is controlled by providing a gas behind the substrate to enhance heat transfer rates across the microscopic gaps between the substrate and the surface of the chuck. The electrostatic chuck can be supported by a base which has channels for passing a fluid therethrough to cool or heat the chuck. Once a substrate is securely held on the chuck, process gas is introduced into the chamber and a plasma is formed to process the substrate by CVD, PVD, etch, implant, oxidation, nitridation, or other processes.
During processing, a substrate is often subjected to non-uniform processing rates or other processing properties across the substrate surface. For example, such non-uniform processing can give rise to concentric processing bands in the radial direction across the substrate surface. Non-uniform processing can also result from the distribution of gas species or plasma species in the chamber. For example, the distribution of gas across the chamber can vary depending on the location of the inlet gas ports and exhaust ports in the chamber relative to the substrate surface. Also, mass transport mechanisms can alter the rates of arrival and dissipation of gaseous species at different regions of the substrate surface. Variability in processing rates can also arise from non-uniform heat loads occurring in the chamber. Such variable heat loads can also occur, for example, due to non-uniform coupling of energy from the plasma sheath to the substrate or radiant heat reflected from chamber walls. Such processing variability across the substrate is undesirable as the active and passive electronic devices being fabricated at different regions of the substrate, for example, the peripheral and central substrate regions, can have different properties.
Accordingly, it is desirable to reduce the variations in processing rates and other process characteristics across the substrate surface during processing. It can also be desirable to control temperatures at different regions across the processing surface of the substrate. It is further desirable to control a temperature and gas distribution profile across the substrate during its processing.